Potentiometer



R. HOFFMAN POTENTIOMETER Oct. 31, 1967 Filed Feb. 18, 1965 INVENTOR.

- Lf 2 10 JL 1 \l j il L7 1 205687" HOFFMAN United States Patent F 3,350,672 POTENTIOMETER Robert Hoffman, 17 Copper Beach Place, Merrick, N.Y. 11566 Filed Feb. 18, 1965, Ser. No. 433,725 Claims. (Cl. 338-132) ABSTRACT OF THE DISCLOSURE A potentiometer adapted to be mounted on a chassis and having a plurality of electrically non-conductive wafers arranged in spaced relation to each other disposed within the case. The wafers have a plurality of electrically conductive resistance paths thereon. A plurality of electrical contact tips are mounted on the wafers and integral with the resistance paths. Resistance selector mechanisms are mounted on the case so that each of the selector mechanisms engages one of the electrical contact tips on the corresponding non-conductive wafer. The selector mechanisms have adjustment means located thereon for selective engagement with one of the resistance paths. A rotatable shaft is journalled in the case. A wiper head is provided with conductive elements which bear against the resistance paths. Means are afiixed to the wiper head and the conductive elements for transmitting electrical impulses to insulated connection lugs on the case. There are also means extending outwardly of the case for rotating the rotatable shaft within the case to vary the resistance output of the potentiometer.

The present invention relates generally to variable electrical resistance means, and in particular to a potentiometer containing a large number of selectively variable resistance circuits which may be employed independently or simultaneously.

The concept of the present invention is briefly summarized to include in a potentiometer a plurality of elec trically non-conductive wafers having resistance paths thereon. A plurality of electrically conductive contact tips are integral with the paths and are adapted to be engaged by resistance selector mechanisms in a novel arrangement of parts.

Numerous potentiometers are commercially available which are formed employing helically wound resistance wire connected to appropriate terminals. A movable electrical contact is made to successive portions of the resistance wire by wiper means which is arranged contiguous to the outer surface of the helically wound wire. The wiper underlies and engages the helically wound resistance wire as it is rotated by a control shaft thereby providing an adjustable stepless output throughout the adjustable positions of the wiper.

Potentiometers generally have a number of characteristics which include, a virtually linear stepless output, a low order of inductance and capacitance to facilitate their use with alternating current circuits. It is important that the potentiometer be operable in a manner such that it will produce little circuit noise during operation, that it have a long life with minimal wear despite continued adjustment, and that little torque be required to faciliate necessary adjustment.

Accordingly, it is an object of the present invention to provide a potentiometer having a capacity for selection of a large number of resistance fibers employing a novel means for selection of the desired circuits of a predetermined calculated resistance while at the same time providing a potentiometer having a capacity of numerous independent circuits which may be employed simultaneously or independently.

3,350,672- Patented Oct. 31, 1967 A further object of this invention is to provide a single potentiometer having means therein permitting independent selection of a predetermined resistance without the necessity of providing a multiplicity of independent otentiometers.

Further, it is an object of the present invention to provide a potentiometer having great flexibility in the selection of resistance circuits available within a single potentiometer wherein the wire wound helical resistance Windings are eliminated and;

Further, it is an object of the present invention to provide a potentiometer employing a multiplicity of etched wafers, each wafer having a plurality of different resistance paths thereon for selectively employing a chosen resistance path.

Further, it is an object of the invention to provide a potentiometer having a number of novel resistance selecting terminal posts for selective engagement of a particular resistance path on a particular wafer within the potentiometer.

Still further, it is an object of the present invention to provide a selective terminal post of a novel construction having as an integral part thereof a spring mounted sole projection for releasable engagement with one of the several resistance circuits provided on one of the wafers for variable resistance.

Still further, it is an object of the present invention to provide a terminal post selector rod having a rotatable sole plate for engagement with the resistive elements on the wafers.

Still further, it is an object of the present invention to provide a wafer having a multiplicity of conductive resistive elements are applied to said wafer for the purpose of conducting electrical currents on a non-conductive surface, which resistive elements will serve in a superior manner than the heretofore known helical wire wound resistance elements.

Further, it is an object of the present invention to provide in a single unit a large combination of electrical and mechanical valves, thereby reducing the number of individual potentiometers which must be installed in an electrical device and in thereby serving to reduce the overall size of the component.

Still further, it is an object of the present invention to provide a resistance circuit comprised of resistive films on non-conductive wafers which can be adjustably connected to terminal parts for completion of electrical circuits. I

Further, it is an object of this invention to provide a potentiometer having a plurality of non-conductive wafers surrounding a rotating shaft where the wafers have resistive circuits thereon so that the rotation of the shafts will selectively vary the resistance within one or more circuits.

Still further objects, features and advantages of this invention reside in the provision of a variable potentiometer having a plurality of resistance circuits contained therein which will be inexpensive to manufacture, simple to use and which yield the unexpected advantage of being small in size and suited to perform as if several independent potentiometers were used.

These, together with the various ancillary objects and features of the present invention, which will become apparant as the following description proceeds, are attained by this potentiometer, preferred embodiments of which have been illustrated in the accompanying drawing, by way of example only, wherein:

FIG. 1 is a side elevational view, with parts broken away of the potentiometer demonstrating features of the present invention, with the cylindrical case sectioned to reveal the contents thereof;

FIG. 2 is a transverse sectional view taken along the plane of line 2-2 of FIG. 1;

FIG. 3 is an enlarged sectional detail view of a modified terminal post selector rod for electrically connecting the wafers with the resistance circuits thereon to an appropriate terminal; and

FIG. 4 is an enlarged sectional detail view of another embodiment of terminal post selector rod and control having a rotatable end section for engagement with the chosen resistance circuit on one of the wafers.

With continuing reference to the accompanying drawings, wherein like reference numerals designate similar parts throughout the various views, reference numeral is used to generally designate an embodiment of the potentiometer which is the subject of the present invention. The potentiometer 10 is formed with a cylindrical case or cover 12 having a threaded assembly 14 which may be used to secure the potentiometer to an electrical component or to a chassis housing as may be necessary or desired (not shown). A rotatable shaft 16 extends inwardly from the outside of the potentiometer through the central opening in the threaded assembly 14 past the end wall 18 adjacent the threaded assembly 14 and through the potentiometer housing terminating in a rear end Wall 20. The front end of the rotatable shaft 22 terminates in a knob receiving portion to which a knob 24 is affixed by conventional means. The rotatable shaft 16 is secured within the potentiometer housing against lateral movement by a pair of end thrust bearings 26, 28 which are secured to the rear wall 20 and the shaft 16. A pair of end thrust bearings 30, 32 are secured to the front wall 18 for the purpose of further preventing any lateral movement of the shaft 16.

A plurality non-conductive stationary wafers 36, 38, 40 and 42 are inserted within the cylindrical case 12 and are secured therein by known means such as force fitting, bonding or the like to the interior of the cylindrical case 12. Resistance paths 52', 54', 56 are bonded into surfaces 44, 46, 48, 50 of wafers 36, 38, 40', 42 which resistance paths are formed of an electrically conductive material. Extending through each of the wafers 36, 38, 40, 42, are electrical contact tips 52, 54, 56 which electrical contact tips are integral with the resistance paths 52', 54', 56 respectively the contact tips being narrowed extensions of the resistance films.

Affixed to and extending outwardly from the rotatable shaft 16 are a plurality of Wiper holding arms 60, 62

which wiper arms terminate in non-conductive wiper heads 64, 66 which are rotatable by rotation of the shaft 16. The wiper head 64 is provided with spring metal contacts 70 and 72 which spring metal contacts contact the electrical contact film 52, 54, 56. Wiper head 66 is likewise provided with spring metal contacts 74, 76. Spring metal contacts 76, 72, 74, 76 are connected to contact heads 80 individually. The individual contact heads 80 contact electrically conductive insulated bushings 82 which are affixed to the rotatable shaft 16. A conductor 84 extends from the insulated bushing 82 to solder lugs 86 on the outer surface of the potentiometer cover or casing 12.

Affixed to and extending through the outer surface of the cover or casing 12 are a series of resistance selector mechanisms 90, 92, 94-, 96 which resistance selector mechanisms serve to allow the selection of an individual resistance path on one of the respective wafers. The resistance selector mechanisms 90, 92, 94, 96 are formed with selector contact tips 98 which tips are mounted on selector rods 100. The selector rods 100 pass through sleeves 102 and have adjustment means for the purpose of allowing the selection of the desired resistance path by advancing the selector rod 100 with the contact tips 98 inwardly or outwardly so that the contact tip 98 will engage the desired resistance paths 52, 54, 56.

Solder lugs 106 are connected to the selector mechanisms 90, 92, 94, 96 so that the individual electrical circuits through the potentiometer can be completed and the potentiometer wired into the electrical circuit.

The advancement of the selector mechanisms 90, 92, 94, 96 can be clearly seen by reference to FIG. 1 and in particular to noting the position of selector mechanism 94 and 96 wherein selector mechanism 94 engages resistance path 54' while selector mechanism 96 engages resistance path 56.

A plurality of secondary selector mechanisms which are designated at 91, the other of these mechanisms not being shown in the drawings, are likewise adjustable to engage one of the resistance paths 52, 54', 56' on the wafer forming the second leg of the circuit.

Further, a plurality of taps designated as 99 are provided which may be used for completion of the circuit in conjunction with the solder lugs 86, which taps will then form the third leg of the circuit instead of the solder lugs 86.

In operation in order to vary the resistance within the potentiometer for a given circuit the knob 24 is rotated by the user, the rotatable shaft 16 turns Within the potentiometer thereby simultaneously rotating the wiper holding arms 60, 62 and the non-conductive wiper heads 64, 66. As the wiper heads 64, 66 are rotated by the rotation of the shaft 16 the spring metal contacts 70, 72, 74, 76 are moved while in continuous contact with the resistance paths 52', 54', 56 on the respective wafers. As the wiper heads 64, 66 are rotated the resistance of the circuits in the potentiometer are increased or decreased in a smooth, stepless manner depending on the direction of the rotation. Rotation stop means 108 are provided on each of the respective wafers to prevent the complete rotation of the wiper heads and possible misalignment of the contact springs.

Referring now specifically to FIG. 3 there is shown a modified form of a resistance selector mechanism wherein the resistance selector mechanism generally designated as and has a sleeve 122 which is adapted to be soldered into the outer cover of a potentiometer. A selector sole tip 124 which is adapted to fit into and bear against the contact tip on a wafer is attached to or integrally formedwith a spring portion 126 which extends inwardly toward the sleeve and is part of the selector rod 128. The rearward portion 130 of the selector rod 128 is formed with projections or ridges 132 so as to provide for easier gripping and adjustment. The shaft 128 has a through bore 134 extending therethrough. A telescoping capsule like assembly 136 having an upper portion 138 and a lower portion 140 is sized to fit within the through bore 134. A compression spring is placed with the capsule-like assembly 136 and urges the upper portion 138 and the lower portion 140 away from each other. The sleeve 122 is provided with a series of dome-shape cutouts 144.

When the selector rod 128 is inserted within the sleeve 122, the upper portion 138 and the lower portion 140' are compressed toward each other so as to permit 111- sertion of the selector rod 128 into the sleeve 122. As the selector rod 128 is advanced inwardly toward the center of the potentiometer the capsule-like assembly 136 will expand as it reaches the dome-shape cutouts within the sleeve 122. The walls of the d0me-shape cutouts serve as cam surfaces and the spring 142 within the capsule-like assembly 136 will position the sole plate 124 in alignment with one of the resistance paths where it will be maintained by the spring tension of spring 142. Position locating markers 146 are provided on the rear portion 130 of shaft 128 for the purpose of providing visible means for telling which resistance path the selector rod sole is in contact with.

Referring now specifically to FIG. 4 there is illustrated a further modified form of a resistance selector mechanism generally designated as 200 and has a sleeve 202 which is adapted to be soldered into the outer cover of a potentiometer. A circular selector tip 204 is revolvably mounted between the bifurcated arm 206 on the inner end of the selector rod 208. Extending between the bifurcated arms 206 and through the center of circular selector tip 204 is an axle 210 which permits the circular selector tip 204 to revolve. A spring collar 212 is affixed to the sleeve 202 and has extending rearwardly and downwardly therefrom a spring 214 which spring is adaptful to engage the rearward portion 216 of the shaft 208. A series of gooves 220 are provided in the shaft 208 rearward of the sleeve 202 into which the tip 218 of the spring will fit as the selector rod 208 is advanced forward or rearward within the potentiometer casing. The grooves 220 are so placed that when the tip 218 of the spring 214 seats within the groove the selector tip 204 Will be in alignment with one of the resistance contact tips on the wafer Within the potentiometer.

It is to be noted that if it isso desired one or more circuits of the potentiometer can be employed as resistor means merely by utilizing two of the three legs of the resistance circuit without any additional modifications of the potentiometer circuit or design.

Further, it is to be understood that in lieu of using the selector mechanisms 90, 91, 92, 93, 94, 95, 96, 97 for the purpose of isolating the chosen resistance paths, such isolation may be obtained by selective employment contact tip 70. The contact tip 70 may be electrically isolated to terminate in separate terminal posts on the housing so as to create electrical conductivity between the wiper and the posts. The proper terminal post would then be selected in order to obtain the desired resistance path.

A latitude of modification, change and substitution is intended in the foregoing disclosure, and in some instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the spirit and scope of the invention herein.

I claim:

1. A potentiometer comprising a case, a plurality of electrically insulative wafers disposed within said case, said wafers each having a plurality of conductive resistance paths thereon, a plurality of electrical contact tips mounted on said wafers integral with said resistance paths, means mounting a plurality of individual resistance selector mechanisms on said case so that each of said selector mechanisms engages one of said electrical contact tips on the corresponding wafer, said selector mechanisms having adjustment means located there-on for selective engagement with one of said contact tips, wiper means engaging said resistance paths, and means for rotating said wiper means to vary the resistance output of the potentiometer.

2. A potentiometer according to claim 1, wherein said wiper means includes a wiper head provided with a plurality of conductive elements, said conductive elements bearing against said resistance paths.

3. A potentiometer according to claim 1, wherein said wafers are fixed in said case in spaced relation to each other.

A potentiometer according to claim 1, including threaded means on said case for detachably securing said potentiometer to a chassis.

5. A potentiometer according to claim 1, wherein said wafers are disc shape in configuration.

6. A potentiometer according to claim 1, wherein said selector mechanisms includes means for adjusting and holding the position of said selector mechanisms in discrete predetermined positions.

7. A potentiometer comprising a case, an electrically insulative wafer disposed within said case, said wafer having a plurality of conductive resistance paths thereon, electrical contact tip means mounted on said wafer integral with said resistance paths, resistance selector means, means mounting said resistance selector means on said case so that said resistance selector means engages said electrical contact tip means, wiper means engaging said resistance paths, and means for rotating said wiper means to vary the resistance output of the potentiometer said wiper means including a wiper head provided with a plurality of conductive elements, said conductive elements bearing against said resistance paths.

8. A potentiometer according to claim 7, including threaded means on said case for detachably securing said potentiometer to a chassis.

9. A potentiometer comprising a case, means on said case for mounting said potentiometer on a chassis, a plurality of electrically non-conductive wafers arranged in spaced relation to each other disposed within said case, said wafers having a plurality of electrically conductive resistance paths thereon, a plurality of electrical contact tips mounted on said wafers integral with said resistance paths, means mounting a plurality of individual resistance selector mechanisms on said case so that each of said selector mechanisms engages one of said electrical contact tips on the corresponding non-conductive wafer, said selector mechanisms having adjustment means located thereon for selective engagement with one of said resistance paths, a rotatable shaft journalled in said case, a wiper head of non-conductive material engaging said shaft, said wiper head being provided with conductive elements, said conductive elements bearing against said resistance paths on said wafers, means afiixed to said wiper head and said conductive elements for transmitting electrical impulses to insulated connection lugs on said case, and means extending outwardly of said case for rotating said rotatable shaft Within said case to vary the resistance output of the potentiometer.

10. A potentiometer according to claim 9, wherein said selector mechanisms includes means for adjusting and holding the position of said selector mechanisms in discrete predetermined positions.

References Cited UNITED STATES PATENTS 2/1952 Owens 338l27 X 9/1953 Coyne et a1. 338-137 

1. A POTENTIOMETER COMPRISING A CASE, A PLURALITY OF ELECTRICALLY INSULATIVE WAFERS DISPOSED WITHIN SAID CASE, SAID WAFERS EACH HAVING A PLURALITY OF CONDUCTIVE RESISTANCE PATHS THEREON, A PLURALITY OF ELECTRICAL CONTACT TIPS MOUNTED ON SAID WAFERS INTEGRAL WITH SAID RESISTANCE PATH, MEANS MOUNTING A PLURALITY OF INDIVIDUAL RESISTANCE SELECTOR MECHANISMS ON SAID CASE SO THAT EACH OF SAID SELECTOR MECHANISMS ENGAGES ONE OF SAID ELECTRICAL CONTACT TIPS ON THE CORRESPONDING WAFER, SAID SELECTOR MECHANISMS HAVING ADJUSTMENT MEANS LOCATED THEREON FOR SELECTIVE ENGAGEMENT WITH ONE OF SAID CONTACT TIPS, WIPER MEANS ENGAGING SAID RESISTANCE PATHS, AND MEANS FOR ROTATING SAID WIPER MEANS TO VARY THE RESISTANCE OUPUT OF THE POTENTIOMETER. 